DS1340Z-33+

Real Time Clock Overview

The DS1340Z-33+ is a low-power real-time clock (RTC) and calendar integrated circuit manufactured by Analog Devices Inc./Maxim Integrated. It operates with a primary supply voltage range of 2.97V to 5.5V and supports a backup supply from 1.3V to 5.5V. The device provides timekeeping for seconds, minutes, hours, day, date, month, and year in binary-coded decimal format. It features an I2C bidirectional serial interface supporting standard (100kHz) and fast (400kHz) modes. Key electrical characteristics include active supply currents up to 300µA at 5.5V and standby currents as low as 150µA. The component is housed in an 8-pin SO package.

Real Time Clock Feature Summary

• I2C Interface: Supports Standard Mode (100kHz) and Fast Mode (400kHz) communication via SDA and SCL pins.
• Trickle Charger: Includes programmable current-limiting resistors (250Ω, 2kΩ, 4kΩ) and diode selection for charging backup batteries or supercapacitors.
• Power Management: Built-in power-fail detect circuit automatically switches between VCC and VBACKUP supplies; includes oscillator stop flag.
• Clock Calibration: Features software-adjustable calibration bits allowing frequency compensation of +4.068ppm or -2.034ppm per step.

Real Time Clock Applications

• Portable Instruments
• Point-of-Sale Equipment
• Medical Equipment
• Telecommunications

Real Time Clock Procurement Notes

Verify the specific suffix Z-33+ indicates the 3.3V operating voltage variant in the 8-pin SO package. Confirm RoHS compliance status (+ denotes lead-free). Check manufacturer documentation for end-of-life notices, as some DS1340 variants have been discontinued. Ensure ordering specifications match the required voltage range and package type.

Real Time Clock Selection Notes

Select the DS1340Z-33+ when a 3.3V nominal supply is available. For systems requiring lower voltage operation, consider the DS1340Z-18+ (1.8V) or DS1340Z-3+ (3.0V) variants. If space constraints require an integrated crystal, the DS1340C series offers a 16-pin SO package with an onboard oscillator. Verify that the external pull-up resistors on SDA and SCL are compatible with the desired I2C speed and bus capacitance limits.

Real Time Clock Part Context

The DS1340Z-33+ belongs to the DS1340 family of RTCs, which are pin-compatible and functionally equivalent to the ST M41T00. The 'Z' suffix typically denotes a lead-free/RoHS-compliant package, while '+33' specifies the 3.3V supply version. This component serves as a drop-in replacement for legacy RTC designs requiring I2C connectivity and trickle-charging capabilities.

Real Time Clock Replacement Considerations

The DS1340 is explicitly noted as being pin-compatible and functionally equivalent to the ST M41T00. Other variants within the same family, such as DS1340Z-18+ and DS1340Z-3+, offer different voltage ranges but share the same interface and register map. The DS1340C series provides similar functionality with an integrated crystal in a larger package.